Idiopathic retroperitoneal fibrosis (IRF) is a rare condition hallmarked by the presence of a retroperitoneal mass consisting of chronic inflammatory infiltrate and abundant fibrous tissue. IRF usually presents as a systemic inflammatory disease, with constitutional symptoms (e.g. fatigue, weight loss) and high acute-phase reactants; in addition, IRF patients often complain of abdominal or lumbar pain and, if ureteral involvement is present, they may also show oliguria and symptoms related to uremia.